Throttle actuating mechanism



Jalb 27, 1959 D. D. STOLTMAN 2,871,001

THROTTLEl ACTUATING MECHANISM Filed May 9, 1957 TTORNEY.

` quired to open the secondary throttle.

United States Patent O THROTTLE ACTUATING MECHANISM Donald D. Stoltman, Rochester, N. Y., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application May 9, 1957, Serial No. 658,112

6 Claims. (Cl. 261--23) The `present device relates to a throttle actuating mechanism for a carburetor. More specifically this device relates to a multi-barrel or compound type carburetorhaving primary and secondary throttles in which the primary throttle is adapted to` be opened in advance of the secondary throttle and further in` which the secondary throttle is opened in response to the quantity of air ilowing through the primary induction passage.

In the present device a servo or power mechanism is adapted to actuate the secondary throttle in response to a vacuum force which is proportional to the quantity of air flowing through the primary induction passage and which type throttle operation is generally well known in the carburetor field. However, there has existed a problem of accurately cont-rolling the actuation of the secondary throttle in view of the magnitude of the vacuum force available to control the throttle in the desired manner.

In general, `it is desirable to provide means for retaining the secondary throttle in a closed position during the initial operation of the primary throttle with the sec ondarythrottle being opened after the air flow through the primary induction passage indicates mixture requirements in excess of the latters capacity. One of the problems with this type of power or vacuum control has been, how-` ever, that once the secondary throttle begins to open the quantity of air liowing through the primary induction passage is reduced and therefore the vacuum force which is utilized to operate the secondary throttle is diminished under conditions when more rather than less force is re- The present invention is directed to a unique device which permits the fullopening of the secondary throttle by providing means which progressively diminishes the resistance to the opening ofthe secondary throttle in proportion to its degree of opening in such a way as to result in a net `increase in the torce tending to opensuch throttle with an increase in engine demand.

The details of the present invention as well as other objects and advantages thereof are set forth in the detailed description which follows.

in the drawing:

Figure l is a partially sectioned elevational view of a carburetor embodying the subject invention; and

Figures 2 an-d 3 are diagrammatic views showing in detail theoperation of the subject invention.

A` carburetor is shown generally at 1Q and is of the type generally shown and described in Olson 2,771,282. The present carburetor differs from that of the Olson patent in the manner in which the primary and secondary throttles are controlled `and it is with regard tothis difference that the present description will be directed.

Carburetor iti includes primary and secondary induction passages l2 and 11i. A choke valve 16 is disposed in the primary induction passage 12 and is adaptedto be lcontrolled by an automatic choke mechanism as set forth in the aforenoted Olson application. A throttle valve 18 is mounted in the primary induction passage posteriorly of a main venturi 26. A similar throttle valve 22 is disposed inthe secondary induction passage 14 and is adapted to be Acontrolled byamechanism `now to be described.

The secondary throttle valve 22 is fixed for rotation upon a shaft 2410 which is also fixed a bell ,crankV type lever 26 having arms Z8 and 30. A servo mechanism 32 is mounted upon the carburetor throttle body 34 through a suitable bracket 36. The servo includes a pair of casing members 38 and 4t) between which a iiexible diaphragm member 42 is peripherally clamped. Reinforcing discs 44 are attached centrally of the diaphragm 42 and have a rod 46 fixed thereto. Rod 46 is adapted to project through an enlarged sleeve 4S supported in aligned openings in casing 'member 4t) and bracket 35 in such a way that the chamber Si) dened by diaphragm 42 `and casing 40 is open to the` atmosphere. between rod 46 and arm 28 of lever 26.

A fitting 5d is mounted on servo casing 3S and is` adapted to connect a conduit Sti with a similar fitting 58 threadably mounted on the throttle body 34. A passage 60 is suitably formed in the carburetor l@ and is adapted to communicate with the main venturi 20 of the primary inductionpassage 12. In this way it is apparent that as the quantity of air flowing through the primary induction passage increases a vacuum force will be created in passage 60 which increases with the increase in primary induction passage air flow. This vacuum force is transmitted from passage GtiA to conduit 56 and to a chamber 62 defined by casing member 3h anddiaphragm d2 such that a vacuum force acts on the diaphragm tending to move the latter as well as rod 46, link f5.2 and lever 26 in a clockwise direction tending to open the secondary throttle 22.

inasmuch as it is desired to maintain the secondary throttle in a closed position until the primary induction passage can no longer supply enough combustible mixture to satisfy the needs of the engine, a spring device indicated generally at 66 is provided. rEhe spring device 66 includes a link 68 fixed to arm Sti of lever 26 at 70 and a low rate tension spring member 72 connected between the other end "ld of link 68 and the servo supporting bracket 36 at 75. Spring mechanism 65 is connected to lever 26 so as to lexert a throttle closing force which acts in opposition to the vacuum opening force of the servo mecha nism 32. in other words, the spring closing force and the vacuum opening force act throughlmoment arms disposed generally on opposite sides of the secondary throttle shaft axis.

As best seen in Figure 2, which assumes the primary induction passage is supplying suiilcient combustible mixture to satisfy engine demand, with the throttle 22 in a` `closed lposition the force of spring will act through a moment arm to maintain the throttle closed against the vacuum force extant in servo chamber 62. As the 'ow through the primary induction passage increases to a Value causing the vacuum in chamber 62 to open the secondary throttle 22 against the action of spring 72, it will be apparent that the rotation of the lever 26 with the throttle 22 will shorten the moment arm through which the spring 72 may act. This diminution of the spring moment arm continues as the throttle opens from its closed or zero de- `grec position to `some partially open position, illustrated as a 40 position. Between the zero and 40 positions it is apparent that end 7i) of link 68 has been rotating relative to lever arm 3i? and that the Spring 72 is under a tensile force. in moving from the zero to 40 position it is further apparent that the spring moment arm has progressively decreased from that :shown at 80 to that shown at with the result that the net resistance of spring 72 to the opening of the secondary throttle 22 is progressively decreased consistent with the decrease in the vacuum force in passage dil available to open the secondary throttle. While, as noted, spring 72 has a low rate it is apparent that as lever 26 rotates in a clockwise direction tending to stretch the spring the latter will increasingly resist opening of the.` throttle 22, However, the

A link 52 is articulated low rate of spring 72 coupled with the decreasing moment arm, as described, and an increasing moment arm, as will subsequently be described, through which the servo force is acting result in a net increase in the secondary throttle opening force as engine demand increases,

In 4order that throttle `22 begin opening quickly once the primary induction passage l2 has reached its mixture supplying capacity, it is necessary to have the throttle closing force of springmechanism 66 correspondingly decrease rapidly. As already noted this is achieved in part by a decrease in the moment arm through which spring 72 acts on lever 26. Accordingly, it is necessary to incline arm 30 of lever 26 from an imaginary vertical line through the axis of shaft 24 to approximately the extent shown in Figures 1 and 2. Thus a line-of-centers through the rotative axis of the secondary throttle and the point of connection 7i) of link 63 and arm 30 is inclined from the vertical away from the servo 32. In this way the point of connection 70 between link 68 and lever 26 is so disposed that the rotation of the latter lever will cause an initially high rate of decrease in the spring moment ann and a corresponding rapid initial opening rate of throttle 22. lt is apparent that if arm 30 of lever 26 were vertical the initial opening movement of throttle 2-2 would initially cause very little change in the spring moment arm.

So inclining arm 30 of lever 26 for proper opening of throttle 22 creates a secondary problem in that spring 72 and link- 68 will pass overcenter with respect to the axis of shaft 24 unless means is provided for preventing this action. The undesirability of the link and spring going overcenter is apparent in that both the servo 32 and the spring 72 would then be acting to open throttle 22 and there would be no means for closing the throttle once it had fully opened. ln other words, it is necessary to prevent the spring moment arm from decreasing from positive to a negative value which would otherwise reverse the springs action on valve 22.

To prevent the throttle closing force passing overcenter a tang 86 is formed on arm 39 of lever 26 and projects transversely of the arm in such a way as to be engaged by link 68 when the throttle valve and lever have moved to the partially open position represented by the 40 position, as best seen in Figure 3. Upon link 68 engaging tang 86, the link is no longer able to pivot or rotate relative to the lever 26 and further opening movement of the secondary throttle places the link under a bending stress. Referring to Figure 3, when link 68 tiret engages the tang 86, as has been characterized by a 40 opening of the secondary throttle, the moment arm through which spring 72 acts to oppose `opening of the secondary throttle 22 is indicated at 82. With further opening of the secondary throttle 22 the bending force imposed on link 63 will cause end 74 to pivot upwardly relative to the spring and in so doing progressively increase the moment arm through which the spring acts during the remaining `opening movement of the secondary throttle. Thus, throughout the entire opening range of the secondary throttle 22 the tensile force acing on the spring '72 continuously increases. However, as noted and for reasons yet to be discussed, other control factors are also changing to insure proper opening of throttle 22 with the vacuum force available.

If it is desiredto further reduce the force tending to close throttle 22, link 68 could be made flexible so as to bend `after it engages tang 56 and in this way further decrease or at least not increase the spring moment arm subsequent to such engagement. It such a modification were made it is'apparent that tang 86 might have to be moved toward the axis of shaft 2li to prevent the Spring force from passing over-center with respect to said axis and the connection ot` said spring to the carburetor.

The connection of link 52 to arm 2li of lever 26 also bears an important relationship to the actuation of the secondary throttle 22 as thus far described. As seen in Figure 2,4 with the secondary throttle in a closed position,

link 52 acts through a moment arm 90 to initiate opening movement of the secondary throttle. As the secondary throttle opens under the influence of the vacuum in chamber 62 the moment arm progressively increases toward a maximum indicated at 92 which represents substantially full open position of the secondary throttle.

The increase in moment arm from to 92 through which the throttle opening force of servo 32 acts coupled with the initial decrease in the moment arm through which spring 72 acts is such as to compensate for the decreased vacuum in servo chamber 62, any rate change in spring 72 and the subsequent increase in the spring moment arm to insure the full and timely opening of the secondary throttle 22.

It is apparent that the gures in degrees which have been utilized to describe the various positions of the throttle 22 and lever 26 are merely for illustrative purposes and in no way constitute a limitation on the present invention. These gures may be changed to suit the type of actuation desired with any particular carburetor. In addition, it is possible to structurally modify the present throttle actuating mechanism within the scope of the invention as set forth in the appended claims.

I claim:

l. A carburetor comprising a primary air induction passage, a venturi formed in said induction passage, a primary throttle valve disposed in'said induction passage posteriorly of said venturi, a secondary induction passage, a throttle valve disposed in said secondary passage, a lever xed'for rotation with said secondary induction passage throttle, a servo mechanism mounted on said carburetor, a conduit connecting said servo mechanism with the venturi of the primary induction passage, linkage means connecting said servo mechanism with said lever whereby the servo will tend to open said Secondary throttle as the ilow of air through said venturi increases, spring means xed at one end to said carburetor and at the other end to said lever tending to urge the secondary throttle in a closed direction, said spring means being connected to said lever such that the moment arm through which said means acts to close said secondary throttle progressively decreases as the throttle moves from a fully closed to a partially opened position, said linkage means being connected to said lever such that the moment arm through which said servo mechanism acts to open said secondary throttle progressively increases from the fully closed position of said throttle to a substantially fully opened position ot said throttle, said spring means and said linkage means being arranged with respect to said lever so that the resultant force tending to open said secondary throttle increases from the fully closed to the fully opened position of said secondary throttle.

2. A carburetor comprising a primary air induction passage, a venturi formed in said induction passage, a primary throttle valve disposed in said induction passage posteriorly of said venturi, a secondary induction passage, a throttle valve disposed in said secondary passage, a lever fixed for rotation with said secondary induction passage throttle, a servo mechanism mounted on said carburetor, a conduit connecting said servo mechanism with the venturi of the primary induction passage, linkage means connecting said servo mechanism with said lever whereby the servo will tend to open said secondary throttle as the flow of air through said venturi increases, spring means xed at one end to said carburetor and at the other end to said lever tending to urge the secondary throttle in a closed direction, the point of connection between the spring means and the lever being adapted during the opening movement of the secondary throttle to pass overcenter with respect to the rotative axis of the secondary throttle and the point of connection of the spring means with the carbureor, means for preventing the lever actuating force of said spring means from passing over-center, said linkage means being connected to said lever such that the moment armV through which `said servofmechanism acts to open said secondary throttle progressively increases from the fully closed position of said throttle to a substantially fully opened position of said throttle, said spring means and said linkage means being arranged with respect to said lever that the secondary and primary throttles reach fully opened positions at substantially the same time.

3. A carburetor comprising a primary air induction passage, a venturi formed in said induction passage, a primary throttle valve disposed in said induction passage posteriorly of said venturi, a secondary induction passage, a` throttle valve disposed in said secondary passage, a lever xed for rotation with said secondary induction passage throttle, a servo mechanism mounted on said carburetor, a conduit connecting said servo mechanism with the venturi of the primary induction passage, linkage means connecting said servo mechanism with said lever whereby the servo will tend to open said secondary throttle as the iiow of air through said venturi increases, spring means fixed at one end to said carburetor and 'at the other end to said lever tending to urge the `secondary throttle in a closed direction, said spring means being connected to said lever such that the moment arm through which said means acts to close said secondary throttle progressively decreases as the throttle moves from a fully closed to a partially opened position, said lever including an element adapted to engage said spring means when said throttle reaches said partially opened position to arrest the decrease of said spring moment arm, said linkage means being connected to said lever such that the o moment arm through which said servo mechanism acts to open said secondary throttle progressively increases from the fully closed position of said throttle to a substantially fully opened position of said throttle, said spring means and said linkage means being so arranged with respect to said lever so that the resultant force tending to open said secondary throttle increases from the fully closed to the fully opened position of said secondary throttle. i

4. A carburetor `comprising a primary air induction passage, a venturi formed in said induction passage, a primary throttle valve disposed in said induction passage posteriorly of said venturi, a secondary induction passage, a throttle valve disposed in said secondary passage, a lever fixed for rotation with said secondary induction passage throttle, a servo mechanism mounted on said carburetor, a conduit connecting said servo mechanism with the venturi of the primaryinduction passage, linkage means connecting said servo mechanism with said lever whereby the servo will tend toopen said secondary throttle as the flow of air through said venturi increases, spring means xed at one end to said carburetor and at the other end to said lever tending to urge the secondary throttle in a closed direction, said spring means being connected to said lever such that the moment arm through which said means acts to close said secondary throttle progressively decreases as the throttle moves from a fully closed to a partially opened position, means associated with said secondary throttle for preventing said moment arm from decreasing to a negative value, said linkage means being connected to said lever such that the moment arm through which said servo mechanism a-cts to open said secondary throttle progressively increases from the fully closed position of said throttle to a substantially fully opened position of said throttle, said spring means and said linkage means being so arranged with respect to said lever so that the secondary and primary throttles reach fully opened positions at substantially the same time.

5. A carburetor comprising a primary air induction passage, a venturi formed in said induction passage, a primary throttle valve disposed in said induction passage posteriorly of said venturi, a secondary induction passage, a throttle valve disposed in said secondary passage, a lever iixed for rotation with said secondary induction passage throttle, a servo mechanism mounted on said carburetor, a conduit connecting said servo mechanism with the venturi of the primary induction passage, linkage means connecting said servo mechanism with said lever whereby the servo will tend to open said secondary throttle as the ilow of air through said venturi increases, and a spring mechanism adapted to urge said secondary throttle toward a closed position, said spring mechanism comprising a link articulated at one end to said lever and a spring anchored at one end to said carburetor and articulated at the other end to said link, said spring mechanism being connected to said lever such that the moment arm through which said mechanism acts to close said throttle progressively decreases as said throttle moves from a fully closed to a partially open position, the end of said link articulated to said lever being adapted to rotate relative to said lever between the fully closed and partially open positions of said secondary throttle, said lever including a tang projecting therefrom and adapted to engage said link intermediate the ends thereof when said secondary throttle moves to said partially open position, said tang being adapted to support said link against relative rotation with respect to said lever as the throttle moves from said partially opened to a fully opened position and to thereby arrest the decrease in the spring moment arm, said spring means and said linkage means being so arranged with respect to said lever so that the primary and secondary throttles reach fully opened positions at substantially the same time.

6. A carburetor comprising a primary air induction passage a venturi` formed in said induction passage, a primary` throttle valve disposed inl said induction passage posteriorly of said venturi, a secondary induction passage, a throttle valve disposed in said secondary passage, a bell crank lever ixed for rotation with said secondary induction passage throttle, a servo mechanism mounted on said carburetor, a conduit connecting said` servo mechanismL with the venturi of the primary induction passage, linkage means connecting said servo mechanism `with said lever whereby the servo will tend to open said secondary throttle as the flow of air through said venturi increases, and a spring mechanism adapted to urge said secondary throttle toward a closed position, said spring mechanism comprising a link articulated at one end to said lever and a spring anchored at one end to said carburetor and articulated at the other end to said link, a line-of-centers through the rotative axis of the secondary throttle and point of connection of said link and lever being inclined from the vertical away from said servo, said spring mechanism being connected to said lever such that the moment the arm through which said mechanism acts to close said throttle progressively decreases at a high initial rate as said throttle moves from a fully closed to a partially open position permitting a fast initial opening of the secondary throttle, the end of said link articulated to said lever being adapted to rotate relative to said lever between the fully closed and partially open positions of said secondary throttle, said lever including a tang projecting therefrom and adapted to engage said link intermediate the ends thereof when said secondary throttle moves to said partially open position, said tang being adapted to support said link against relative rotation with respect to said lever as the throttle moves from said partially opened to a fully opened position, said spring means and said linkage means being so arranged with respect to said lever so that the resultant force tending to open said secondary throttle increases from the fully closed to the fully opened position of said secondary throttle.

References Cited in the le of this patent UNITED STATES PATENTS Bicknell June 2, 1953 Armstrong r.- Apr. 30, 1957 Carlson et al. Apr. 30, 1957 

